DESCRIPTION: The objectives of this project are to investigate the role of DNA methylation on the regulation of the SOD2 gene, a putative tumor suppressor gene, which encodes the antioxidant enzyme manganese superoxide dismutase (MnSOD). While it is generally accepted that in malignant cells SOD2 is expressed at lower levels than in normal cells, the mechanisms underlying this differential expression are not known. However, numerous studies have pointed to the participation of tumor suppression genes whose expression is modulated by genomic methylation patterns, and which are believed to contribute to differentiation and carcinogenesis. The central hypothesis of this project is that cytosine methylation in the CpG islands surrounding the SOD2 gene transcription start site can adversely influence the expression of SOD2. Specific aim #1 is to map the human SOD2 gene for cis-acting regulatory elements that participate in governing its expression. In specific aim #2, the hypothesis will be tested that hypermethylation of CpG island in the human SOD gene promoter can block the expression of a reporter gene in a non-malignant cell line known to express SOD2 (the WI-38 human lung fibroblast cell line). I specific aim #3 the hypothesis will be tested that a decreased SOD2 expression in cancer cells relative to their normal cell counterparts is due to differential methylation of the SOD2 promoter. Specific aim #4 is to determine the effects of methylation and transcription factor availability on the transcriptional activation of the SOD2 promoter in malignant and non-malignant cells. A better understanding of the mechanisms of regulation of the expressio of SOD2 during carcinogenesis and differentiation may lead to new strategies for the treatment of diseases in which aberrant SOD2 expression plays a key role.